Question

What are Oxidation states in elements?

Answer 1

The number of electrons gained or lost by an atom is defined as the Oxidation State of that element. Oxidation States are mainly studied by the help of electronic configuration. Oxidation states simplify in determining what is being oxidized or reduced.

Complete answer:
The oxidation state of an atom is the total number of electrons which can be removed (which produces a positive oxidation state) or added to an element (producing a negative charge) to reach its present state.
An increase in oxidation state means Oxidation and decrease in oxidation state is Reduction. This simple key helps in understanding the concept of Oxidation state. With the change in the oxidation state, we can determine which element is being oxidized or reduced.
Counting the number of electrons transferred can be time consuming in determining the oxidation states. Hence these rules can be followed:
The Oxidation state of neutral or uncombined atoms is always zero. Which means that the O.S of elements regardless of their structure or size $Xe,C{l_2},{S_8}$ is zero.
The sum of oxidation states of all the elements in a compound is zero. So that the overall compound is neutral.
If an ion is present, the sum of the oxidation states of the atoms in the compounds is equal to the charge on the ion.
Remember, the more electronegative atom is assigned negative charge. The less electronegative/electropositive atom has a positive charge. The electronegativity increases across the period and decreases down the group.

Note:
The general oxidation state observed in various elements are given below:
Group I always have $+ 1$ state, Group II (Alkaline earth metals) has $+ 2$ state, Oxygen has a Oxidation state of $- 2$ (except for in peroxide where it is $- 1$ ), Fluorine is the most electronegative element and has the oxidation state of $- 1$ always. Transition metal elements have variable oxidation states.